1. The Field of the Invention
The present invention relates to airbag inflation systems in motor vehicles. More specifically, the invention relates to an airbag venting system for directing inflation gases through an airbag.
2. Technical Background
Inflatable airbags are well accepted for use in motor vehicles and have been credited with preventing numerous deaths and injuries. Some statistics estimate that frontal airbags reduce the fatalities in head-on collisions by 25% among drivers using seat belts and by more than 30% among unbelted drivers. Statistics further suggest that with a combination of seat belt and airbag, serious chest injuries in frontal collisions can be reduced by 65% and serious head injuries by up to 75%. Airbag use presents clear benefits and vehicle owners are frequently willing to pay the added expense for airbags.
A modern airbag apparatus may include an electronic control unit (ECU) and one or more airbag modules. The ECU is usually installed in the middle of an automobile, between the passenger and engine compartments. If the vehicle has a driver airbag only, the ECU may be mounted in the steering wheel. The ECU includes a sensor which continuously monitors the acceleration and deceleration of the vehicle and sends this information to a processor which processes an algorithm to determine if the vehicle is in an accident situation.
When the processor determines that there is an accident situation, the ECU transmits an electrical current to an initiator in the airbag module. The initiator triggers operation of the inflator or gas generator which, in some embodiments, uses a combination of compressed gas and solid fuel. The inflator inflates a textile airbag to impact a passenger and prevent injury to the passenger. In some airbag apparatuses, the airbag may be fully inflated within 50 thousandths of a second and deflated within two tenths of a second.
An airbag cover, also called a trim cover panel, covers a compartment containing the airbag module and may reside on a steering wheel, dashboard, vehicle door, vehicle wall, or beneath the dash board. The airbag cover is typically made of a rigid plastic and may be forced open by the pressure from the deploying airbag. In deploying the airbag, it is preferable to retain the airbag cover to prevent the airbag cover from flying loose in the passenger compartment. If the airbag cover freely moves into the passenger compartment, it may injure a passenger.
Airbag apparatuses have been primarily designed for deployment in front of the torso of an occupant between the upper torso of an occupant and the windshield or instrument panel. Conventional airbags, such as driver""s or passenger airbags (hereinafter referenced as the xe2x80x9cprimary airbagxe2x80x9d), protect the occupant""s upper torso and head from colliding with a windshield or instrument panel.
Airbag apparatuses are generally designed under the assumption that the occupant is riding in the vehicle in a forward facing seated position with both feet on the vehicle floor. When an occupant is not in this position the occupant or occupant""s body part is said to be xe2x80x98out of position.xe2x80x99 As an occupant occasionally is xe2x80x98out of positionxe2x80x99, airbag apparatus designs which are effective regardless of the occupant""s position are advantageous.
In an accident situation involving a primary airbag, there are three phases which follow each other between the beginning of the accident and the end. In the inflation phase, the goal is to fully inflate the primary airbag to occupy a majority of space between an instrument panel and an occupant before the occupant moves significantly forward in the vehicle compartment. In this phase, the primary airbag fully inflates in response to a signal from the ECU within about 50 thousandths of a second.
Next, there is the impact phase in which the goal is to impact the occupant""s body in such a manner as to reduce injuries to the occupant. Generally, a flat, soft surface best accomplishes the goal of this phase. The primary airbag and the occupant""s upper torso collide. The primary airbag and occupant""s upper torso then react to each other in response to the collision.
Finally, the last phase is the deflation phase. The goal in this phase is to bring the occupant""s upper torso to a resting state without allowing the upper torso to collide with other rigid structures in the vehicle. The goal is accomplished by releasing the gas which inflated the primary airbag at a rate which is slower than the speed at which the occupant""s body is moving forward.
Airbag apparatuses seek to meet the goals of all three phases. Meeting the goals of the inflation and deflation phases is the most challenging. Airbag apparatus designs must function within tight parameters of physics in order to protect a vehicle occupant involved in an accident. During a front end collision, if the occupant is restrained by a seat belt, the occupant""s upper torso bends at the waist and hits the primary airbag. Airbag apparatuses are generally small compact units which are capable of presenting the inflated primary airbag in front of a vehicle occupant before the occupant""s upper torso moves significantly forward. Because of the short time interval between the start and end of an accident situation, the primary airbag must be inflated very rapidly. The high inflation rate causes the front surface of a conventional primary airbag to travel to within inches of an xe2x80x98in positionxe2x80x99 occupant""s upper torso at a rate around 200 miles per hour.
Most airbags provide a release for the gas within the airbag. This release is called venting. By venting the gas in the primary airbag, the impact forces of the occupant""s torso are absorbed.
The venting of gas from the primary airbag should fall within certain timing parameters. First, the venting should not occur too early in the accident sequence. Second, the venting rate should not be too slow.
If venting occurs too early, such as during the inflation phase, then the primary airbag may be under inflated at the time of impact with the occupant. An under inflated bag provides less restraint and increases the likelihood of impact between the occupant and the interior of the vehicle. If a primary airbag vents gas too slowly, then the airbag may be too rigid to effectively protect the occupant.
When an occupant collides with the primary airbag, the occupant""s body compresses the gas within the airbag. If there is no release of gas, then the compression stops and the textile bag presents a rigid structure resisting the forward movement of the occupant""s body. But, if the airbag has structure to provide the desired rate of venting then the impact force of the occupant is transferred to gas inside the airbag. The gas reacts by pushing against other gas within the airbag. This forces gas out the vent structure at the desired rate. The force of impact is transferred to the gas within the airbag and then to the air outside the airbag. The desired rate of venting is reached by forming holes in the airbag. These holes may be half circle cuts in the bag, tear seams, multiple holes, or other like release mechanisms placed in the bag to ensure that the desired venting rate is reached and held constant during the deflation phase.
A constant venting rate results in fewer injuries to the occupant. A constant venting rate also allows the airbag to slow the occupant""s body at a constant rate. The restraining force which the airbag is placing on the occupant is constant. The occupant""s body is better able to withstand restraining forces when they are applied constantly over time.
Airbag apparatuses are installed in various different vehicles which convey occupants of varying shapes and sizes. One occupant may fit the optimal xe2x80x98in positionxe2x80x99 requirements while another may not. Therefore, airbag designs which meet the goals of the three phases must accommodate for the variety among vehicle and occupants. Multi-chamber airbag apparatuses have been developed to accommodate the variations.
A multi-chamber airbag apparatus is one in which there are two or more chambers within the airbag which are inflated during the inflation phase. Dividers within the airbag form the chambers. The dividers are generally made of the same textile material as the airbag. Multiple chambers allow the airbag to reach full inflation at a similar rate as a single chamber airbag. But, the airbag""s front surface is not traveling toward the occupant as rapidly. Therefore, injuries to occupants, including those xe2x80x9cout of position,xe2x80x9d may be less severe.
Generally in a multi-chamber airbag apparatus, inflation of each chamber is accomplished by openings in the chamber dividers. The inflator is connected in a conventional manner. The multi-chamber airbag apparatus has holes in the dividers to allow gas to pass from one chamber to the next. A first chamber surrounds the inflator. Once the first chamber is substantially filled, the gas moves through the holes to the one or more other chambers until the whole airbag is inflated.
Vents are formed in the multi-chamber airbag to cause the airbag to release pressure once the occupant impacts the airbag. In single chamber and conventional multi-chamber airbags, the vent holes are located such that a direct path exists for the gas to travel between the inflator and the vent holes. A direct path is one in which the gas may leave the inflator and travel directly out of the vent without having to traverse the majority of a particular chamber. The result is that a significant quantity of the gas inflating the chamber may exit through the vent hole rather than completing inflation of the one or more chambers prior to exiting the airbag. This is called pre-mature venting. To compensate for premature venting, more propellant may be used in the inflator. The increase in propellant may require an increase in the size of the inflator which in turn may increase the size of the whole multi-chamber airbag apparatus. A solution to premature venting is to force the gas to travel through all the chambers of the airbag prior to exiting by way of a vent hole.
It is desirable that vent holes be formed in a chamber which is furthest from the inflator. This forces the inflation gas to travel throughout the airbag prior to exiting. This ensures that the inner chambers are completely filled before gas is allowed to escape. Conventional airbags do not channel the inflation gas to eliminate pre-mature venting. Instead, conventional airbags use larger inflators or higher output inflators to compensate for pre-mature venting.
Multi-chamber airbag apparatuses are effective in meeting the goals of the impact phase. As described above, a goal of the impact phase is to present a soft generally flat surface to impact the occupant. A conventional inflated airbag has a convex arced front surface which is presented for impact with the occupant. A non-flat airbag surface creates a tendency for the occupant to slide along the curved surface and off the airbag, particularly when the occupant is unbelted or xe2x80x9cout of position.xe2x80x9d To flatten the arc, various tethering structures have been developed.
A tether is a structure of the airbag apparatus which limits the forward movement of the front surface to a particular distance. Generally, one or more tethers are used to flatten the arc of the airbag front surface. Tethers may be formed from the same textile material as the airbag. Tethers are generally attached to the front surface of the airbag at one end. The other end is attached near the throat or area where the airbag material is attached to a rigid structure such as the inflator, or housing. The body of the tether may be located either internal or external to the airbag. Tethers which are separate members often involve complicated or expensive fastening mechanisms. Such mechanisms include sewing the tether to the airbag, securing the tether with a loop and pin assembly, glueing the tether to the airbag, welding the tether to the airbag, and the like. These mechanisms require skilled workers who know where to attach the tethers and how to operate machines which fasten the tethers. If the tether is a separate member and must be positioned within the airbag then the process of assembling the airbag may be even more complicated than external tethers.
Multi-chamber airbags provide a unique solution to the problems involved with tethers which are installed on the inside of an airbag. Multi-chamber airbag apparatuses generally exhibit tethering functionality because the chamber dividers are connected to the front and rear surface of the airbag. The divider functions as a tether because the front surface is prevented from moving outward beyond the length of the divider. Multi-chamber airbag apparatuses which provide internal tethering do exist. However, these apparatuses do not include an ability to channel the inflation gas within the airbag between the inflator and the vent holes.
Accordingly, it would be an advancement in the art to provide a multi-chamber airbag venting system which reduces the velocity of the front surface of the airbag during the inflation phase of an accident situation. A further advancement in the art would be to provide a multi-chamber airbag venting system which channels inflation gas in series through a plurality of internal chambers such that each chamber is substantially inflated prior to venting of inflation gas. It would be another advancement in the art to provide a multi-chamber airbag venting system which provides internal tethering without complicated fastening of tethers and without requiring high skill of the airbag assembly worker. A further advancement in the art would be to provide a multi-chamber airbag venting system which combines the advantages of multi-chamber airbags which channel inflation gas and multi-chamber airbags which provide simple internal tethers. The present invention provides these advancements in a novel and useful way.
The apparatus of the present invention has been developed in response to the present state of the art, and in particular, in response to the problems and needs in the art that have not yet been fully solved by currently available multi-chamber airbag venting systems. Thus, the present invention provides a multi-chamber airbag venting system which provides channeling of the inflation gas and simple internal tethers to provide a safe inflation phase, generally planar impact surface, and a fully inflated airbag which deforms properly and prevents pre-mature venting.
In one embodiment of a multi-chamber airbag venting system, the system includes a front panel, a rear panel and a middle panel. Each panel is a piece of textile fabric conventionally used in fabricating airbags. The textile material used is a nylon or polyester weave. The front and rear panels are substantially the same size and shape. The front and rear panels are shaped and sized such that once joined along their respective circumferential peripheries and filled with gas the airbag occupies the desired volume of space between the vehicle occupant and the interior of a vehicle. The rear panel includes an airbag mouth. The airbag mouth secures the airbag to the inflator or housing. The airbag mouth also serves as a passage which allows the inflation gas leaving the inflator to enter the airbag.
The middle panel is positioned between the front panel and rear panel. The middle panel is substantially the same size and shape as the front panel and rear panel. Alternatively, the middle panel may be smaller than the front panel and rear panel. The middle panel is connected to the front panel and rear panel along their respective circumferential peripheries. The middle panel divides the interior of the airbag into a first chamber behind the middle panel and a second chamber in front of the middle panel. Alternatively, the middle panel may be connected to the front panel and rear panel in any manner which divides the interior of the airbag into at least two chambers. The middle panel includes one or more middle panel passage holes. The middle panel passage holes are disposed along the perimeter of the middle panel. Alternatively, the middle panel passage holes may be disposed at any point in the middle panel within the circumferential periphery which secures the middle panel to the front panel and rear panel.
The system further includes vent holes. A vent hole is a hole in the airbag which allows the gas inside the airbag to escape. A first vent hole is disposed in the rear panel. A second vent hole is disposed in the middle panel. The first vent hole and second vent hole are of substantially the same size. The first vent hole and second vent hole are sized to provide the desired venting rate. To ensure the airbag does not vent too quickly, the vent holes are sized in proportion to the volume of the airbag. The first vent hole and second vent hole are attached to each other to form a vent passage. A vent passage allows gas to escape from a chamber in the airbag to an area external to the airbag.
In alternative embodiments, the system may also include a plurality of middle panels between the front panel and rear panel wherein each additional panel divides the interior into an additional chamber. Alternatively, a plurality of vent passages may be formed by a plurality of first vent holes and a plurality of second vent holes. In a further alternative embodiment, the middle panel may include a plurality of middle panel passage holes.
In further embodiments, the system includes a tether. A tether is a structure formed by connecting the middle panel to a portion of the front panel and connecting the middle panel to a portion of the rear panel. The tether restricts the distance the front panel travels away from the inflator once inflated. Alternatively, the system may include a plurality of tethers which restrict the distance the front panel travels during inflation.
The system may also include a second tether. The second tether is formed by connecting the middle panel to a portion of the rear panel. The second tether serves to restrict the distance the middle panel travels during inflation.
The system may also include a restrictor and a central restrictor. The portion of the front panel connected to a portion of the middle panel forms a central restrictor. The portion of the rear panel connected to a portion of the middle panel forms a restrictor. The central restrictor may be located at substantially the center of the front panel. The restrictor may include the first vent hole and second vent hole discussed above. The connections of the panels which form the central restrictor and restrictor may be formed by weaving, sewing, glueing or welding the two panels together at points where the restrictor is desired.
In the preferred embodiment of a multi-chamber airbag venting system, the components are sized and configured for use in a vehicle driver and/or passenger airbag. The front panel, rear panel, and middle panel may be shaped to accommodate the volume between the vehicle occupant and the vehicle interior.
These and other features, and advantages of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.